1. Field of the Invention
The present invention relates to a conductive organic/inorganic complex composition, a method of preparing the composition, a thin conductive organic/inorganic complex film prepared using the composition, an organic electroluminescent device comprising the thin conductive organic/inorganic complex film, and a method of manufacturing the organic electroluminescent device. More particularly, the present invention relates to a conductive organic/inorganic complex composition which is hydrophobic and insoluble in water and an organic solvent, has a high mechanical strength, and is thermally and chemically stable, and of which compositional composition can be changed over a wide range, a method of preparing the composition, a thin conductive organic/inorganic complex film prepared using the composition, an organic electroluminescent device comprising the thin conductive organic/inorganic complex film, and a method of manufacturing the organic electroluminescent device.
2. Description of the Related Art
Organic electroluminescent devices are self-emissive display devices using a phenomenon that when electrical current is applied to a fluorescent or phosphorescent organic layer, electrons and holes are combined in the organic layer to emit light. Organic electroluminescent devices have advantages such as light weight, simple constitutional elements, easy fabrication process, and high image quality and color purity. Further, they can realize moving pictures perfectly and can be operated at low power consumption. Thus, vigorous research is being conducted on the organic electroluminescent devices.
In the above organic electroluminescent devices, the organic layer may be a single emission layer. However, in general, the organic layer is an organic multi layer comprising a hole injection layer (HIL), an electron transport layer (ETL), a hole transport layer (HTL), and an emission layer (EML), etc., in order to increase efficiency and decrease a driving voltage. Such a multi layer may generally include 11 a hole-related layer, an electron-related layer, and an emission layer. FIG. 1 is a schematic cross-sectional view of a conventional organic electroluminescent device (in the case of using a low molecular weight emission layer). Referring to FIG. 1, the conventional organic electroluminescent device has a structure in which an anode 12 is layered on a substrate 11 and a hole injection layer 13 and a hole transport layer 14 as hole-related layers are sequentially layered on the anode 12, an emission layer 15 is layered on the hole transport layer 14, an electron transport layer 16 and an electron injection layer (EIL) 17 as electron-related layers are sequentially layered on the emission layer 15, and a cathode 18 is layered on the electron injection layer 17.
In the conventional organic electroluminescent device, O2 diffusion occurs in an anode, for example, made of indium tin oxide (ITO) and the anode has a low work function of 4.7 to 4.8 and has a rough surface. In order to overcome these problems, a conductive polymer, for example, water-soluble polyaniline, polypyrrole, or polythiophene, for example, polyethylenedioxythiophene (PEDOT) was used in a hole injection layer or a buffer layer.
FIG. 2 is a schematic view illustrating quenching in an organic electroluminescent device which does not comprise a hole injection layer or a buffer layer. FIG. 3 is a schematic view illustrating quenching in an organic electroluminescent device which comprises a hole injection layer or a buffer layer 33.
Referring to FIG. 2, quenching occurs on an ITO electrode 22 in the device which does not comprise a hole injection layer or a buffer layer. Referring to FIG. 3, quenching occurs on the hole injection layer or buffer layer 33 containing a conductive polymer in the organic electroluminescent device which comprises the hole injection layer or buffer layer 33.
The device illustrated in FIG. 2 has a structure in which an emission layer 25 is directly coated on the ITO electrode 22 and has low performance of device due to the problems induced by ITO, as described above. In FIG. 2, reference numerals 28 and 29 denote a cathode and an emissive region, respectively. To overcome the problems, the device illustrated in FIG. 3, a conductive polymeric material, for example, polyaniline, polypyrrole, or PEDOT/PSS is used in the hole injection layer 33 formed on an ITO electrode 32. In FIG. 3, reference numerals 35, 38, and 39 denote an emission layer, a cathode, and an emissive region, respectively. However, the conductive polymeric material is hydrophilic, has a high water uptake, is highly soluble in water or an organic solvent, and binds to electron to form a salt and induce sulfate diffusion.